1. Field of the Invention
The invention relates to a liquid crystal display; in particular, to a source driver and its receiver applied in the liquid crystal display using two grounded nodes in the second-stage circuit of the two-stage amplifier to shut down the two transistors coupled to the two nodes respectively, and a switch controlled by a delay control signal is disposed between the two nodes to achieve the aims of saving power and not increasing wake-up time.
2. Description of the Prior Art
In general, the source driver of the liquid crystal display includes a plurality of receivers arranged in series. When one of the receivers receives a start signal, it is the receiver's turn to receive gray level data. In order to save power, other receivers not receiving gray level data will usually enter into a power-saving mode. When the receiver almost finishes the receiving of gray level data, the receiver will output a wake-up signal to the next receiver to wake up the next receiver from the power-saving mode to start to receive the gray level data.
Please refer to FIG. 1. FIG. 1 illustrates a function block diagram of the receiver of the source driver in the prior art. As shown in FIG. 1, the receiver 1 of the source driver of the conventional liquid crystal display usually includes a structure of two-stage operational amplifier 10 having a first-stage amplifying circuit 100 and a second-stage amplifying circuit 102, and the open-circuit operation is used to amplify differential signals and convert them into single-ended signals. And then, the single-ended signals will be converted into Transistor-Transistor Logic (TTL) signals by a full-swing buffer 12, and the TTL signals will be outputted by a voltage output end 124 for pushing the next stage circuit.
When the receiver 1 of the conventional source driver is under the power-saving mode, the receiver 1 not only uses a transistor switch MP5 to cut off the current source 14 in the first-stage amplifying circuit 100, but also disposes a transistor switch MN5 for cutting off current to achieve the effect of saving power. However, under the normal operation mode, since the receiver 1 of the conventional source driver includes additional transistor switch MN5 having on-resistance, the swing of the amplified voltage signal Vop outputted by the two-stage operational amplifier 10 will become smaller due to the on-resistance of the transistor switch MN5.